This Application is related to an Application entitled, xe2x80x9cFlexible Telecommunications Switching Networkxe2x80x9d being filed by C. J. Chrin and M. J. Zola, concurrently, with this Application, and assigned to the same assignee.
This invention relates to digital telecommunications switching systems, and more specifically, to narrowband and broadband digital telecommunications switching systems.
Problem
As is well known, the demands for telecommunications services are changing rapidly. Many of these demands are for services such as video, which require a much broader band than the conventional audio band. The combination of cable television distribution systems with telephone and other customer premises equipment telecommunications systems, is making more and more available a loop plant capable of transmitting broadband signals to individual customers. At the same time, the development of switching systems which handle both broadband and narrowband signals in an efficient and integrated way, has not kept pace with this demand. Accordingly, a problem of the prior art is that there is no satisfactory large switching system for processing both narrowband and broadband traffic efficiently and an integrated fashion.
Solution
The above problem is solved, and an advance is made over the prior art in accordance with this invention, wherein a core central network receives inputs in a standard format from a plurality of connecting modules, and switches these signals among the modules. In order to handle a large amount of broadband traffic efficiently, these signals each carry a substantial number of base band channels combined into a single signal. In accordance with Applicant""s preferred embodiment, the standard signal is a signal that carries 2.048 Mb per second payload, the equivalent of 32 DS0 voice channels. Each such signal is switched through the central core entity without changing the information in the payload.
In accordance with one feature of Applicants"" invention, when a narrowband signal, i.e., a single voice channel, is to be switched through the core, this narrowband signal occupies only a single DS0 payload, with the rest of the signal being occupied by xe2x80x9cfillxe2x80x9d bits. Advantageously, this allows individual voice channels to be switched through the central core from any connected module to any other connected module.
In accordance with Applicants"" preferred embodiment, the modules connected to line and trunk signals convert these signals into standard format signals. These modules include a microprocessor based switch, wherein the microprocessor receives input pulse code modulated signals generated by standard line and trunk interface cards, and converts these into standard intermediate stage signals, and switches signals from particular lines and trunks to a standard signal destined for the appropriate module at the other end. In addition, output interface units for interfacing between facilities such as SONET/SDH, (Synchronous Optical Network/Synchronous Digital Hierarchy) facilities, and the cores which are connected to the core switch, with the conununications being the standard signals. These output interface units convert between the standard signal and an ATM, or IP signal, for transmission over virtual channels of the SONET facilities.
The standard signals in this embodiment are VT2 signals and carry 32 64 Kbit channels, and are further characterized in the discussion of FIGS. 17-20.
Advantageously, using 1999 technology, a core network for supporting 12288 (768xc3x9716), VT2 signals, can be housed on a single custom silicon chip. This is a great advantage compared to disbursing this circuitry over many chips, since intra-chip connections do not require interface circuits, and can use the very narrow circuit interconnection lines allowable on a silicon chip. Advantageously, by allowing one narrowband signal to occupy to a full VT2 signal on a full interconnectivity among modules connected to the core network, is possible without requiring the core network to switch anything other than VT2 signals.
In accordance with another feature of Applicants"" invention, connections to prior art modules is made possible. Prior art modules such as the communication module of a 5ESS(copyright) switch, manufactured by Lucent Technologies Inc., communicate via proprietary link signals, which are encapsulated at the input of the core network into VT2 signals. These NCT links can carry both narrowband and broadband signals. The communication module can be connected to a switch module of a 5ESS(copyright) switch.
In accordance with another aspect of Applicants"" invention, a group of modules are interconnected by a plurality of center stage modules as in a Clos network, a well-known arrangement for guaranteeing absence of blocking from any input to any output. Advantageously, a large non-blocking network is made feasible by this arrangement.